A Simplified Approach to Risk Assessment Based on System Dynamics: An Industrial Case Study

Seveso plants are complex sociotechnical systems, which makes it appropriate to support any risk assessment with a model of the system. However, more often than not, this step is only partially addressed, simplified, or avoided in safety reports. At the same time, investigations have shown that the complexity of industrial systems is frequently a factor in accidents, due to interactions between their technical, human, and organizational dimensions. In order to handle both this complexity and changes in the system over time, this article proposes an original and simplified qualitative risk evaluation method based on the system dynamics theory developed by Forrester in the early 1960s. The methodology supports the development of a dynamic risk assessment framework dedicated to industrial activities. It consists of 10 complementary steps grouped into two main activities: system dynamics modeling of the sociotechnical system and risk analysis. This system dynamics risk analysis is applied to a case study of a chemical plant and provides a way to assess the technological and organizational components of safety.     

SOME QUALMS ABOUT THE TEST OF THE INSTITUTIONALIST HYPOTHESIS OF THE LONG-RUN BEHAVIOR OF VELOCITY

This paper expresses econometric qualms about Bordo and Jonung's [1981] analysis of long-run velocity. They did not recognize that, for U.S. and Canadian data, the log of velocity has a unit root. Hence, estimation of a log level regression may produce spurious regressions.
When Bordo and Jonung's velocity equation is reestimated in rate of change form, permanent income is significant, contrary to their earlier conclusion. Moreover, using this approach gives a stronger result for one of the institutional variables in the velocity function, in the sense that the remaining variables become more significant.     

On the Deng-Lin random number generators and related methods

We study the structure and point out weaknesses of recently proposed random number generators based on special types of linear recurrences with small coefficients, which allow fast implementations. Our theoretical analysis is complemented by the results of simple empirical statistical tests that the generators fail decisively. Directions for improvement and alternative generators are also pointed out.     

Besoins individuels et collectifs: Nanacatlan,Mexico

The author intends both to describe a native credit institution in a peasant community and to analyse its overt and covert functions. The community fund, managed by the local authority (presidencia auxiliar) is theoretically available to all household heads who can show solvency (e.g., by pawning a piece of property, usually land). Apart from assisting peasants who face a shortage of cash, another overt function of the system is to finance, with the interests which are paid back on the loans, the functioning of the local administration. Because of the great economic discrepancies between peasants (50 per cent of them own no land, while 2.5 per cent own 30 per cent of the land) one real, although covert, function of the credit institution is to channel a substantial amount of cash to the local upper class (which has little access to banking facilities). Therefore it actually enhances their economic domination over the majority of villagers, which fact allows us to understand the strict control they have exerted over the management of the fund since its foundation, some 40 years ago.